Technology known as OpenFlow is disclosed in Non-Patent Literatures (NPLs) 1 and 2. In OpenFlow, communication is taken as end-to-end flow, and path control, recovery from failure, load balancing and optimization are performed in flow units. An OpenFlow switch functioning as a forwarding node is provided with a secure channel for communication with an OpenFlow controller and operates in accordance with a flow table for which appropriate addition or rewriting is prescribed by the OpenFlow controller. The flow table has definitions of sets of: rules (FlowKey, matching key) for matching with packet headers, actions (Action) defining processing content, and flow statistical information (Stats), for each flow.
FIG. 12 shows an example of action name(s) and action content(s) defined in Non-Patent Literature 2. OUTPUT is an action to output a packet to a designated port (interface), and SET_VLAN_VID to SET_TP_DST are actions to modify fields of a packet header.
For example, on receiving a first packet, the OpenFlow switch searches for an entry having a rule (FlowKey) that matches header information of the received packet, from the flow table. As a result of the search, in a case where an entry matching the received packet is found, the OpenFlow switch implements processing content described in an action field of the entry in question, with regard to the received packet. On the other hand, as a result of the search, in a case where an entry matching the received packet is not found, the OpenFlow switch forwards the received packet to the OpenFlow controller via the secure channel, requests determination of a packet path based on source and destination of the received packet, receives a flow entry realizing this, and updates the flow table.
Thus, in OpenFlow, fine grained path control for each flow is possible, but flow entry configuration load increases due to increase in the number of flows. Therefore, with technology disclosed in Non Patent Literatures 1 and 2, there is a risk that the load for setting of flow entries will become large, when application is made to a large scale network.
Non Patent Literature 3 discloses a solution strategy for this problem. Non Patent Literature 3 describes a list of processes to be performed in packet header parts by respective OpenFlow switches, instead of defining an entry for each flow, with regard to a flow table provided in a normal OpenFlow switch. In this way, the abovementioned problem is solved.
For example, as shown in FIG. 11, for each OpenFlow switch an action where the switch may be executed is defined, and an address is attached to each action. With regard to a packet, embedded in the packet header is a series of pointers indicating addresses of actions to be executed by the respective OpenFlow switches according to a series of OpenFlow switches passed through. The OpenFlow switches perform forwarding by reading the pointer series in the packet header and calling respective actions to be executed thereby. According to this method, it is possible to forward packets without setting flow entries when a packet is received, and it is possible to reduce delay upon forwarding.
On the other hand, Patent Literature (PTL) 1 describes technology related to packet forwarding in a large scale network. Patent Literature 1 describes a route calculation method of high calculation efficiency, in a large scale network formed by a plurality of domains. The method described in Patent Literature 1 defines the domains hierarchically, and deploys a PCE (Path Calculation Element) in the respective hierarchical domains Route calculation is performed for each layer; an upper level PCE determines input and output nodes for lower level domains; the route calculation is executed in parallel by requesting the lower level domains to perform calculation tasks; and the route calculation is provided in a network formed by a plurality of domains.    PTL 1:    Japanese Patent Kohyo Publication No. JP2009-539156A    NPL 1:    Nick McKeown, and seven others, “OpenFlow: Enabling Innovation in Campus Networks,” [online] [search conducted Feb. 7, 2011], Internet<URL:http://www.openflowswitch.oredocuments/openflow-wp-latest.pd.    NPL 2:    “OpenFlow Switch Specification” Version 1.0.0. (Wire Protocol 0x01) [search conducted Feb. 7, 2011], Internet<URL:http://www.openflowswitch.org/documents/openflow-spec-v1.0.0.pd.    NPL 3:    Chiba, Yasunobu, and two others, “A Proposal of Flow Entry Reduction Scheme for Flow-based Networks and Its Implementation on OpenFlow-based Network,” The Institute of Electronics, Information and Communication Engineers, Technical Report, Vol. 109, No. 448, NS2009-163, pp. 7-12.